U.S. patent application number 10/575508 was filed with the patent office on 2008-06-19 for confidential viewing system utilizing spatial multiplexing.
This patent application is currently assigned to WATERSTRIKE INCORPORATED. Invention is credited to David A. Struyk.
Application Number | 20080144967 10/575508 |
Document ID | / |
Family ID | 39535763 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080144967 |
Kind Code |
A1 |
Struyk; David A. |
June 19, 2008 |
Confidential Viewing System Utilizing Spatial Multiplexing
Abstract
An apparatus and method for providing confidential viewing of a
fundamental image on an image display device utilizing spatial
multiplexing image modification, whereby fundamental image
components of the fundamental image are spatially multiplexed or
combined with appropriately determined inverted image components
thereof, and aligned with adjacent display regions/pixels of an
image display device so as to neutralize the fundamental image and
generate a combined image that appears substantially featureless to
the naked eye. The display pixels aligned with the fundamental
image components are cross-polarized relative to the adjacent
pixels aligned with the inverted image components, thereby
providing for extraction of the fundamental image by an authorized
viewer wearing appropriate eyewear polarized to correlate with the
state of polarization of the pixels aligned with the fundamental
image components. Enhanced security may be provided by utilizing a
variable polarizer to alter the state of polarization of the
respective display regions, or by altering the position of
fundamental and inverse image components to align with differently
polarized display regions. Extraction of the fundamental image may
then be accomplished by using active polarized eyewear synchronized
to correlate in polarization with the pixels aligned with the
fundamental image components.
Inventors: |
Struyk; David A.;
(Deephaven, MN) |
Correspondence
Address: |
SCHROEDER & SIEGFRIED, P.A.
15600 WAYZATA BOULEVARD, SUITE 200
WAYZATA
MN
55391
US
|
Assignee: |
WATERSTRIKE INCORPORATED
Excelsior
MN
|
Family ID: |
39535763 |
Appl. No.: |
10/575508 |
Filed: |
March 30, 2005 |
PCT Filed: |
March 30, 2005 |
PCT NO: |
PCT/US2005/010807 |
371 Date: |
April 13, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60557901 |
Mar 30, 2004 |
|
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Current U.S.
Class: |
382/276 |
Current CPC
Class: |
G09G 3/20 20130101; G09G
3/3611 20130101; G09G 3/001 20130101 |
Class at
Publication: |
382/276 |
International
Class: |
G06K 9/36 20060101
G06K009/36 |
Claims
1. An apparatus for confidential viewing of a fundamental image
utilizing spatial multiplexing image modification, comprising: (a)
an image display device comprising a plurality of adjacent display
regions of different polarization states. (b) a plurality of
spatially multiplexed fundamental image components and related
masking image components derived from said fundamental image
components being displayed on said image display device in
association with said display regions and in such arrangement as to
render said fundamental image components substantially
indecipherable to the naked eye; (c) said fundamental image
components being representative of a fundamental image and being
associated with said display regions having a common state of
polarization that is different than the state of polarization of
said display regions with which said masking image components are
associated; and (d) an image viewing device having polarization
means cooperating with said image display device for allowing
extraction and viewing only of said fundamental image components
from said image display device.
2. (canceled)
3. The confidential viewing apparatus of claim 1, wherein at least
some of said masking image components are the derived inverse of
corresponding said fundamental image components displayed
therewith, and the display of said fundamental and masking image
components on said image display device generates a combined
neutral image that appears substantially featureless to the naked
eye.
4. The confidential viewing apparatus of claim 3, including overlay
image components displayed in association with said masking image
components such that an overlay image appears to the naked eye as
being overlaid upon said substantially featureless image.
5. The confidential viewing apparatus of claim 1 or 3, wherein the
display of said fundamental image components and said masking image
components on said image display device are positionally alternated
in time.
6. The confidential viewing apparatus of claim 1, wherein said
fundamental image components are positionally altered in time to
associate with separate sets of said display regions having
differing polarization states.
7. The confidential viewing apparatus of claim 1, wherein at least
said fundamental image components are time multiplexed with derived
inverse image components thereof.
8. The confidential viewing apparatus of claim 1, wherein both said
fundamental image components and said masking image components are
time multiplexed with derived inverse image components thereof.
9. The confidential viewing apparatus of claim 8, wherein each of
said masking image components is the derived inverse of a
corresponding fundamental image component associated with the same
said display region.
10. The confidential viewing apparatus of claim 1, wherein said
polarization states of said display regions are fixed.
11. The confidential viewing apparatus of claim 1, wherein said
polarization states of said display regions are variable.
12. The confidential viewing apparatus of claim 11, wherein each of
said display regions include a variable polarizer capable of
altering the state of polarization thereof.
13. The confidential viewing apparatus of claim 12, wherein said
variable polarizer is comprised of an electrically-controlled
liquid crystal device.
14. The confidential viewing apparatus of claim 1, wherein said
different polarization states of said display regions are generally
orthogonal to one another.
15. The confidential viewing apparatus of claim 1, wherein at least
some of said display regions are left-hand circularly polarized and
at least some of said display regions are right-hand circularly
polarized.
16. The confidential viewing apparatus of claim 1, wherein said
display regions with which said fundamental image components are
associated are cross-polarized relative to said display regions
with which said masking image components are associated.
17. The confidential viewing apparatus of claim 1, wherein said
image display device is an electronic display device comprising a
plurality of display pixels and having a periodic display refresh
cycle, and wherein each of said display regions includes at least
one of said pixels of said electronic display device.
18. The confidential viewing apparatus of claim 17, wherein said
electronic display device includes a transparent overlay with
designated separate areas of cross-polarized orientations that
align with said pixels to form said plurality of differently
polarized display regions.
19. The confidential viewing apparatus of claim 17, wherein said
fundamental image components and said masking image components are
regenerated upon each said display refresh cycle in association
with a separate set of said pixels having a different polarization
state than that of the next previous said display cycle of said
electronic display device.
20. The confidential viewing apparatus of claim 19, wherein said
image viewing device is comprised of active polarized eyewear which
communicates with said electronic display device to change states
of polarization in sync with said display refresh cycle of said
electronic display device.
21. The confidential viewing apparatus of claim 17, wherein said
display regions of said electronic display device include a
variable polarizing means for altering the state of polarization
thereof, and said image viewing device is comprised of active
polarized eyewear that communicates with said electronic display
device to change states of polarization in sync with changes in the
polarization state of said display regions.
22. An apparatus for confidential viewing of a fundamental image
utilizing spatial multiplexing image modification, comprising: (a)
an image display device comprising a plurality of adjacent display
regions of different polarization states. (b) means for generating
an image on said image display device having a fundamental image
component and a corresponding inverse image component spatially
arranged in association with said display regions so as to form a
combined image that appears substantially featureless to the naked
eye; (c) said image generating means and said image display device
cooperatively communicating so that said fundamental image
component is associated with at least one of said display regions
having a polarization state different than that with which said
inverse image component is associated; and (d) image viewing means
cooperatively polarized with said display regions of said image
display device for allowing viewing only of said fundamental image
component of said combined substantially featureless image.
23. The confidential viewing apparatus of claim 22, wherein said
plurality of display regions are arranged in alternating columns of
different polarization states.
24. The confidential viewing apparatus of claim 22, wherein said
plurality of display regions are arranged in alternating rows of
different polarization states.
25. The confidential viewing apparatus of claim 22, wherein said
combined substantially featureless image is comprised of a
plurality of said fundamental image components and corresponding
inverse image components associated with alternating sets of said
adjacent display regions having different polarization states.
26. The confidential viewing apparatus of claim 22, wherein said
different polarization states of said display regions are generally
orthogonal to one another.
27. The confidential viewing apparatus of claim 22, wherein at
least some of said display regions are left-hand circularly
polarized and at least some of said display regions are right-hand
circularly polarized.
28. The confidential viewing apparatus of claim 22, wherein said
plurality of display regions have fixed polarization states.
29. The confidential viewing apparatus of claim 22, wherein said
plurality of display regions have variable polarization states.
30. The confidential viewing apparatus of claim 29, wherein each of
said display regions comprise an electrically variable
polarizer.
31. The confidential viewing apparatus of claim 30, wherein said
variable polarizer comprises a liquid crystal device capable of
altering polarization state.
32. The confidential viewing apparatus of claim 22, wherein said
image display device constitutes an electronic display device
having a plurality of display pixels, each of said display regions
comprising at least one of said pixels of said electronic display
device.
33. The confidential viewing apparatus of claim 32, wherein said
fundamental image component is associated with at least one of said
pixels having a common polarization state, and said corresponding
inverse image component is associated with at least one of said
pixels having a different polarization state.
34. The confidential viewing apparatus of claim 32, wherein said
electronic display device is configured as a liquid crystal display
device, and each of said display regions includes an electrically
controllable polarizer that is comprised of a liquid crystal device
capable of altering polarization state based on applied voltage
thereto.
35. The confidential viewing apparatus of claim 32, including means
for generating an overlay image visible to the naked eye and
appearing over said substantially featureless image on said
electronic display device, said overlay image having an overlay
image component which is associated with at least one of said
display regions having a polarization state common to that with
which said inverse image component is associated.
36. The confidential viewing apparatus of claim 32, wherein said
electronic display device includes a transparent polarizing overlay
extending over said display pixels, said polarizing overlay being
constructed and arranged to alter the polarization state of some of
said display pixels to generate said plurality of display regions
of different polarization states.
37. The confidential viewing apparatus of claim 22, wherein said
image display device includes a transparent polarizing overlay
constructed and arranged to generate said plurality of adjacent
display regions of different polarization states.
38. The confidential viewing apparatus of claim 22, wherein said
fundamental image component is regenerated anew over time in
association with a different said display region.
39. The confidential viewing apparatus of claim 38, wherein said
different display region has a polarization state different than
that with which said fundamental image component was previously
associated.
40. The confidential viewing apparatus of claim 38, wherein said
corresponding fundamental and inverse image components switch
associated display regions over time.
41. A method for confidential viewing of a fundamental image
utilizing spatial multiplexing image modification, comprising the
steps of: (a) polarizing adjacently positioned display regions of
an image display device with different states of polarization; (b)
displaying spatially multiplexed fundamental image components of a
fundamental image with corresponding inverse image components
thereof on said image display device in such arrangement as to
neutralize and render said fundamental image components
substantially invisible to the naked eye, whereby said fundamental
image components are associated with said display regions having a
state of polarization different than that with which said inverse
image components are associated; and (c) viewing said image display
device through a polarized filtering means that communicates with
said image display device and allows passage and viewing only of
said fundamental image components of said fundamental image.
42. The method of confidential viewing set forth in claim 41,
wherein said step of polarizing said adjacently positioned display
regions of said image display device includes the use of at least
one electrically variable polarizer capable of altering the state
of polarization of at least one of said display regions relative to
other said display regions.
43. The method of confidential viewing set forth in claim 42,
wherein said step of polarizing said adjacently positioned display
regions is carried out with at least one variable polarizer of
liquid crystal construction capable of altering the state of
polarization of at least one of said display regions relative to
other said display regions based on applied voltage to said
variable polarizer.
44. The method of confidential viewing set forth in claim 41,
wherein said step of polarizing said adjacently positioned display
regions of said image display device includes positioning a
polarizing device having separate areas of differently fixed
polarization states in alignment with said display regions of said
image display device.
45. The method of confidential viewing set forth in claim 44,
wherein said step of displaying spatially multiplexed image
components includes varying over time the polarization state of
said display regions with which said fundamental image components
are associated.
46. The method of confidential viewing set forth in claim 41,
wherein said step of displaying spatially multiplexed image
components includes periodically alternating said display positions
of said fundamental image components and said corresponding inverse
image components to appear at differently polarized sets of said
display regions of said image display device.
47. The method of confidential viewing set forth in claim 41,
wherein said step of polarizing adjacently positioned display
regions of said image display device includes arranging said
display regions to alternate spatially between two states of
polarization which are generally orthogonal to one another.
48. The method of confidential viewing set forth in claim 41,
wherein said step of displaying spatially multiplexed image
components includes displaying overlay image components
representative of a separate overlay image on said image display
device, whereby said overlay image components are associated with
at least some of said display regions having a polarization state
common to that with which said inverse image components are
associated.
49. The method of confidential viewing set forth in claim 41,
wherein said step of viewing said image display device utilizes
passive polarized eyewear to allow passage and viewing only of said
fundamental image components of said fundamental image.
50. The method of confidential viewing set forth in claim 41,
wherein said step of viewing said image display device utilizes
active polarized eyewear operating in sync with said image display
device to allow passage and viewing only of said fundamental image
components of said fundamental image.
51. The method of confidential viewing set forth in claim 41,
wherein said step of polarizing adjacently positioned display
regions with different states of polarization includes the use of
right-hand and left-hand circular polarization.
52. The method of confidential viewing set forth in claim 41,
wherein said step of displaying fundamental and corresponding
inverse image components on said image display device generates a
combined substantially featureless image to the naked eye.
53. The method of confidential viewing set forth in claim 41,
including the step of periodically exchanging the display position
of said fundamental and corresponding inverse image components,
while coincidentally altering the polarization state of said
display regions associated therewith so as to maintain a common
polarization state over time for all said display regions
associated with said fundamental image components being
displayed.
54. A method for confidential viewing of a fundamental image
utilizing spatial multiplexing image modification, comprising the
steps of: (a) positioning a transparent polarizing overlay over an
image display device, said overlay comprising a plurality of
adjacently positioned polarizers having different polarization
states; (b) producing a compound image on said display device that
is comprised of a plurality of spatially multiplexed fundamental
image components and masking image components aligned with said
polarizers of said overlay, whereby said fundamental image
components are representative of a fundamental image and said
masking image components are derived from said fundamental image
components, said fundamental image components being aligned with a
group of said polarizers having a common state of polarization
different from that with which said masking image components are
aligned; and (c) viewing said compound image through said overlay
utilizing a lens filter polarized in such manner as to allow
passage and viewing only of said fundamental image components of
said fundamental image.
55. The method of confidential viewing described in claim 54,
including the step of time multiplexing said fundamental and
masking image components with derived inverse image components
thereof.
56. The method of confidential viewing described in claim 55,
wherein said step of viewing said compound image utilizes an active
lens filter capable of altering its state of polarization to match
that of said fundamental image components.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is an application for a patent which is
also disclosed in Provisional Application Ser. No. 60/557,901,
filed on Mar. 30, 2004 by the same inventor, namely David A.
Struyk, and entitled "CONFIDENTIAL VIEWING SYSTEM UTILIZING SPATIAL
MULTIPLEXING," the benefit of the filing date of which is hereby
claimed.
BACKGROUND OF THE INVENTION
[0002] The present invention is related generally to the art of
confidential viewing of display images. More particularly, the
present invention is directed to a confidential viewing apparatus
and method which utilizes techniques of spatial multiplexing image
modification to mask or neutralize a fundamental display image and
render it indecipherable to the naked eye, whereby image decoding
is available only to the intended viewer.
[0003] With the increasing use of video displays for a variety of
systems, such as those used in desktop computers, laptop computers,
televisions, and personal video entertainment systems, there exists
an increasing need and desire to provide confidential viewing of
these displays by only those who the displayed content is intended
for, thus eliminating the possibility of unauthorized viewing.
[0004] Various devices have been introduced over the years to
prevent unauthorized viewing of video displays. The simplest
devices generally include a form of "anti-glare" privacy screen
and/or hoods and shields. These devices are commonly found on
desktop computer displays which are intended to restrict viewing to
only those who are more or less directly in front of the display.
While these are somewhat effective, they cannot prevent viewing by
someone peering over ones shoulder, and thus are far from
secure.
[0005] Other devices have been developed which seek to obscure the
view of a fundamental image from an unintended viewer by
introducing a "masking image." One such device is discussed in U.S.
Pat. No. 5,614,920, which utilizes a flashing screen of light
placed between the video display and the viewer to obscure the
fundamental image. Confidential viewing is provided by utilizing
time synchronized shutter glasses to block the pulses of light and
permit viewing of the fundamental image.
[0006] Other similar devices are disclosed in U.S. Pat. Nos.
5,537,476, and 5,619,219. These devices provide secure viewing of a
display by introducing a secondary masking light or set of
"primary" colors, that are wavelength-shifted from that used to
generate the fundamental image. Secure viewing is provided by
viewing the composite image through specially formulated
narrow-band filtered glasses, which block the wavelength-shifted
image, allowing the fundamental image to pass.
[0007] Still other devices utilize principles of "time
multiplexing" to intermix a masking image with the fundamental
image, thereby obscuring its view from the public. Such systems
usually alternate display frames of masking and fundamental images,
and utilize time synchronized shutter eyewear to decode the
fundamental image. These systems, however, suffer inherently from
display flicker problems, and often incorporate video "flash"
frames which tend to be irritating to the eye. For this reason,
such time multiplexing systems are better suited for a cathode ray
tube (CRT) display, which can operate at significantly faster
refresh rates than a typical liquid crystal display (LCD). Examples
of this type of system can be found in U.S. Pat. Nos. 5,629,984;
5,963,371; as well as Japanese Patent No. 05119754 JP.
[0008] More sophisticated Confidential viewing systems are
disclosed in my two co-pending U.S. patent application Ser. Nos.
10/205,864 and 10/205,866, the contents of which are incorporated
herein by reference thereto. Like those previously described, these
systems involve applications of image multiplexation over time.
However, in this case, principles of color inversion are employed,
whereby the fundamental image is encoded by time multiplexing
itself with an appropriately determined inverted image in such
manner as to produce a neutral, substantially featureless compound
image that may be decoded only with properly synchronized
eyewear.
[0009] In these systems, to provide more enhanced security, the
respective color components of the fundamental image may be encoded
sequentially, thereby requiring more complicated synchronized
variable color-filter decoding eyewear. Such systems are highly
secure and do function to reduce irritating display flicker and eye
strain, since at least one color component of the fundamental image
is always displayed. However, such systems still utilize concepts
of time multiplexing and, although they can be used with LCD's, are
probably better suited for high speed conventional CRT displays at
this time.
[0010] The LCD, however, due to its flat screen, thin profile, high
resolution, and low power consumption, has become the display of
choice for use with most portable laptop computers, where
incidentally, the need for confidential viewing is likely to be the
greatest. In this regard, some devices more specific to the LCD
have been introduced which seek to provide confidential viewing by
removing the top polarizing layer of the LCD screen. This renders
the display "invisible" except to those wearing polarized glasses.
U.S. Pat. No. 5,488,496, issued Jan. 30, 1996, discusses one such
device. Although somewhat effective, this system of confidential
viewing is vulnerable in that anyone wearing properly polarized
glasses, even ordinary Polaroid glasses, can view the hidden image.
Additionally, the screen is not easily converted between
confidential and normal viewing modes. Other devices of this
general type are believed to be disclosed in Japanese Patent Nos.
07084253 JP; 04107524 JP; 02116826 JP; and 05173127 JP.
[0011] With the limitations of the prior art, particularly with
respect to the popular LCD, it is apparent that a better means is
necessary for providing simple, low cost confidential viewing which
can be used in all applications of full color/full motion graphics
and images. Moreover, in order to better accommodate confidential
viewing of today's LCD, it is desirous to accomplish this objective
while avoiding the use of high speed time multiplexing techniques,
or cumbersome, cost-intensive supplemental and/or
wavelength-shifted masking light sources.
[0012] It is believed that my improved image altering apparatus and
method as described hereafter accomplishes this end while
minimizing the cost of implementation and greatly enhancing the
viewing security of video displays today.
BRIEF SUMMARY OF THE INVENTION
[0013] In accordance with the present invention, an apparatus and
method are described herein for providing confidential viewing of a
display image by utilizing techniques of spatial multiplexing image
modification.
[0014] In general, the concept of spatially multiplexing images
involves the process of geometrically combining a fundamental image
with another image on an image display device. If combined with the
appropriate image, spatial multiplexing image modification can be
used for purposes of masking the fundamental image. A periodic (or
random) array of squares, rows, columns, etc., may be removed from
the fundamental image and substituted with corresponding sections
of a masking image, thereby generating a combined image which
obscures the fundamental image from view with the naked eye.
[0015] While it is contemplated that the masking image can be of
any composition capable of rendering the fundamental image
indecipherable, in one embodiment of my invention, the fundamental
image is geometrically combined on an image display device with its
true color-inverted image to produce a combined neutral image that
appears substantially featureless to the naked eye. This is
accomplished by spatially multiplexing fundamental and inverse
image components on an image display device so as to associate with
separate but closely adjacent display regions thereof. As used
herein and throughout the appended claims, the term "adjacent,"
when used in reference to the display regions of an image display
device, is intended to mean nearby, but not necessarily having a
common border.
[0016] These display regions to which the fundamental and inverse
image components correspond are generally associated with, or may
comprise, one or more pixels, or sub-pixels, of a static or dynamic
image display device. As such, they are generally microscopic in
size and are of sufficiently small compass that the human eye has
difficulty distinguishing therebetween. The fundamental and inverse
image components are therefore mixed, neutralizing the fundamental
image and rendering it virtually invisible to the naked eye.
[0017] Creating such a-spatially multiplexed neutral image requires
modification of the original fundamental image to incorporate the
corresponding inverse image components. Generally, for each
fundamental image component utilized, there is required a
corresponding derived inverse image component; thus, each inverse
image component requires displacement of an original fundamental
image component from the fundamental image. The resulting combined
image, then, is essentially comprised of a conglomeration of close,
geometrically-intermixed corresponding fundamental and inverse
image components that, when viewed as a whole with the naked eye,
appears neutral and substantially featureless.
[0018] The multiplexed fundamental image components, albeit hidden
from public view, are representative of the original fundamental
display image. In order to provide confidential viewing of the
fundamental image components, and thus the fundamental display
image, the system is designed such that the display regions of the
image display device with which the fundamental image components
are associated are always cross-polarized (i.e., one polarization
state blocks light admitted by the other) relative to the adjacent
display regions with which the masking image components are
associated. Thus, appropriately polarized eyewear matching the
polarization state of the display regions with which the
fundamental image components are associated will effectively block
all masking image components and allow passage only of the
fundamental image components for confidential viewing. While the
combined multiplexed image renders the fundamental image
indecipherable to the naked eye of the unintended viewer, an
authorized viewer wearing the appropriately polarized eyewear will
have full access to the fundamental image for confidential
viewing.
[0019] Configuring the image display device with adjacent display
regions of differing polarization states may be accomplished
utilizing one of several techniques. In one embodiment, it is
contemplated that a micropolarizing overlay or inlay having closely
adjacent areas of differing polarization states be incorporated
into the image display device. This may be accomplished using
spatially alternating polarized filters, or by using alternating
light retarders to rotate the polarization state of adjacent
display regions. The micropolarizer is constructed and arranged
such that the adjacent areas of different polarization align with
various designated display regions/pixels of the image display
device to alter the polarization state of such display regions to
that of their correspondingly aligned areas of the
micropolarizer.
[0020] In another embodiment, an electrically controllable
polarizer can be incorporated in the image display device to alter
the polarization state of the adjacent display regions. Such an
electrically controllable polarizer may be used in static or
dynamic display systems, and may take the form of a liquid crystal
rotator added to the display configuration in such manner as to
effectively rotate the polarization angle of transmitted light
based on applied voltage thereto. For each display region of the
image display device, the polarization angle can be set to rotate
transmitted light either 0 or 90 degrees, depending on whether such
display region is associated with fundamental or masking image
components.
[0021] Utilizing an electrically controllable polarizer to alter
the state of polarization of adjacent display regions offers
certain advantages in enhanced security. With the ability to now
change states of polarization of individual display regions of the
image display device, it becomes possible to periodically or
randomly alter the state of polarization of the display regions
associated with the fundamental image components. Provided the
polarized eyewear worn by the authorized viewer is synchronized to
change states of polarization in unison with the display regions
associated with the fundamental image components, the polarization
of the eyewear will continue to match that of the fundamental image
components, thereby enabling decoding of the fundamental image. In
this embodiment, mere passive polarized eyewear may no longer be
utilized to decode the fundamental image.
[0022] Notably, a similar effect may also be accomplished in an
electronic display by periodically or randomly altering the display
position of the fundamental image components to align with fixed
areas of polarization different from that with which they were
aligned in the previous display frame(s). In this embodiment,
fundamental image components that are initially suppressed at pixel
locations occupied by the masking image components are revived, and
those fundamental image components previously displayed at other
pixel locations become displaced by new masking image components.
In this mariner, the physical display positions of the respective
fundamental and masking image components are alternated or switched
in synch with the display's refresh rate and in accordance with a
predetermined or random sequence pattern.
[0023] Alternating the display positions of the fundamental and
masking image components in this manner also has the distinct
advantage of increasing image resolution by allowing recapture of
the initially displaced fundamental image components. Rather than
permanently displacing certain fundamental image components,
adjacent fundamental image components may now be alternately
displayed in any desired sequence, thereby allowing full resolution
of the fundamental image to be restored.
[0024] Provided the polarized eyewear worn by the authorized viewer
is synchronized to change states of polarization in unison with the
change of position of the fundamental image components, the eyewear
will still be polarized to match the display regions of the
fundamental image components, thereby enabling same to be decoded.
Again, mere passive polarized eyewear may no longer be utilized to
decode the fundamental image.
[0025] Although less secure, it is also contemplated that the use
of a variable polarizer could be combined to operate in synch with
the alternating display positions of the fundamental image
components, thereby providing a system that may be decoded using
passive polarized eyewear with full resolution of the decoded
fundamental image.
[0026] In the preferred embodiment where inverse image components
are used to mask the fundamental image, more enhanced security may
be obtained by adding to or incorporating as a part of the inverse
image components overlay image components that are representative
of a separate overlay image. By so doing, the fundamental image
components are still neutralized by the corresponding inverse image
components, but the general viewing public will now see a separate
overlay image which may be either static or dynamic, such as in the
case of a movie. The overlay image thus appears "on top" of the
combined substantially featureless image, thereby deceiving
unintended viewers into believing that a different image is being
viewed by the system operator. However, since the overlay image
components are incorporated as part of the inverse image
components, they too will be blocked from the view of the
authorized viewer wearing the appropriately polarized eyewear
matching the polarization state of the display regions associated
with the fundamental image components.
[0027] Although the above illustrations are exemplary of various
means by which an image display device may be configured with
closely adjacent display regions of differing polarization states,
it is contemplated that any means of addressing different
polarization states to adjacent display regions of the image
display device may be utilized for purposes of implementing this
invention.
[0028] As can be seen by the foregoing, through modification of the
fundamental image, corresponding fundamental and masking image
components may be spatially multiplexed for display in association
with adjacent but cross-polarized display regions of an image
display device. From this, with little or no display flicker, a
highly secure combined image may be generated that will render the
fundamental image indecipherable to the naked eye.
[0029] With appropriately polarized eyewear, this combined image
may be demultiplexed for confidential viewing of the fundamental
image. This is accomplished without the need for high speed
multiplexing of image signals, or cumbersome, cost-intensive
supplemental and/or wavelength-shifted masking light sources.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] These and other objects and advantages of the invention will
more fully appear from the following description, made in
connection with the accompanying drawings, wherein like reference
characters refer to the same or similar parts throughout the
several views, and in which:
[0031] FIG. 1 is a diagrammatic representation of an image display
device showing the manner in which such a device may be represented
as a matrix of individual display regions (enlarged for ease of
illustration) that are associated with distinct image components
displayed at various pixel locations, or groups thereof, on the
image display device;
[0032] FIG. 2A is a similar diagrammatic representation of an image
display device showing corresponding fundamental and inverse image
components spatially multiplexed in a checkerboard arrangement of
display regions so as to provide an encoding scheme which produces
a substantially featureless image to the naked eye;
[0033] FIG. 2B is a similar diagrammatic representation of an image
display device showing corresponding fundamental and inverse image
components spatially multiplexed in a row-by-row arrangement of
display regions so as to provide an encoding scheme which produces
a substantially featureless image to the naked eye;
[0034] FIG. 2C is a similar diagrammatic representation of an image
display device showing corresponding fundamental and inverse image
components spatially multiplexed in a column-by-column arrangement
of display regions so as to provide an encoding scheme which
produces a substantially featureless image to the naked eye;
[0035] FIG. 3A is a diagrammatic representation of the image
display device shown in FIG. 2A, where corresponding fundamental
and inverse image components are spatially multiplexed in a
checkerboard arrangement, and polarization encoding is utilized to
make each display region associated with a fundamental image
component cross-polarized relative to the display region associated
with its corresponding inverse image component;
[0036] FIG. 3B is a diagrammatic representation of the image
display device shown in FIG. 2B, where corresponding fundamental
and inverse image components are spatially multiplexed in a
row-by-row arrangement, and polarization encoding is utilized to
make each display region associated with a row of fundamental image
components cross-polarized relative to the display region
associated with the adjacent row of corresponding inverse image
components;
[0037] FIG. 3C is a diagrammatic representation of the image
display device shown in FIG. 2C, where corresponding fundamental
and inverse image components are spatially multiplexed in a
column-by-column arrangement, and polarization encoding is utilized
to make each display region associated with a column of fundamental
image components cross-polarized relative to the display region
associated with the adjacent column of corresponding inverse image
components;
[0038] FIG. 4 is a diagrammatic representation of an image display
device, such as an LCD, incorporating a micropolarizing overlay
having row-by-row alternating cross-polarized areas aligned with
alternating display region rows associated with corresponding
fundamental and inverse image components being displayed
thereon;
[0039] FIG. 5 is a diagrammatic representation of an image display
device, such as an LCD, incorporating an alternative
micropolarizing overlay in the form of a 1/2.lamda. retarder plate
which has row-by-row alternating cross-polarized areas aligned with
alternating display region rows associated with corresponding
fundamental and inverse image components being displayed
thereon;
[0040] FIG. 6 is a diagrammatic representation of an image display
device, such as an LCD, incorporating an electronically
controllable polarizer for altering states of polarization between
adjacent display regions associated with corresponding fundamental
and inverse image components arranged in a row-by-row display
configuration;
[0041] FIG. 7 is a diagrammatic representation of alternating first
and second display frames of an image display device utilizing an
alternate encoding scheme whereby a fixed polarizing overlay is
used in combination with varying display positions of fundamental
and inverse image components, thereby requiring active polarized
eyewear to decode the fundamental image;
[0042] FIG. 8 is a diagrammatic representation of alternating first
and second display frames of an image display device utilizing
still another alternate encoding scheme whereby corresponding
fundamental and inverse image components are time multiplexed with
one another, and a fixed polarizing overlay is used in combination
with varying display positions of fundamental and inverse image
components, thereby requiring active polarized eyewear to decode
the fundamental image; and
[0043] FIG. 9 is a test image encoding breakdown showing the
principles of the encoding scheme described in reference to FIG. 8,
wherein spatial multiplexing and time multiplexing techniques are
combined to vary the polarization states of fundamental image
components over time and recapture full resolution of the
fundamental image upon decoding thereof using active polarized
eyewear.
DETAILED DESCRIPTION OF THE INVENTION
[0044] The present invention, as described and claimed herein,
utilizes principles of spatial multiplexing image modification to
provide for secure confidential viewing of a display image. While
the concepts set forth herein are generally applicable to either
electronic or printed images, the following discussion shall focus
primarily on electronic images, such as those found on video
displays. It shall be understood, however, that print media may be
modified upon printing, using these same spatial multiplexing
techniques, to mask a fundamental image from unauthorized viewing
and provide for confidential viewing only by an intended
viewer.
[0045] In order to better describe my invention, it is helpful to
first explain briefly the concept of "primary color addition" as it
pertains to light produced by video displays, and the response of
the human eye with respect to the same. Virtually all common video
displays, from color television and CRT displays, to LCD screens,
plasma displays, etc., generate an image through the additive
mixture of three primary colors of light: red; blue; and green. A
video display typically has thousands of tiny areas, called pixels,
that produce light of a specific color representative of an image
at that specific location. Each pixel, in turn, is generally
composed of a triad of smaller areas, or sub-pixels, consisting of
tiny phosphors, color filters, or the like, which individually
produce the primary colors red, blue, and green.
[0046] As one views a color image produced on a video display, the
human eye does not detect each red, green, or blue sub-pixel
separately. Rather, depending on the intensity of each primary
color component, the color sensitive cones within the human eye
react to the primary colors, such that one viewing the video
display will see a range of many colors combined to produce the
desired complete image. Thus, depending upon the varying
intensities of light produced by each sub-pixel, the corresponding
pixel will produce a composite light that appears as a different
color to the human eye. If the intensities of all red, blue, and
green components of a given pixel are the same, the human eye will
perceive that the pixel produces a neutral white light. Nearly all
electronically reproducible images are constructed in this
manner.
[0047] For purposes of further discussion herein, as shown in FIG.
1, it is convenient to visualize an image display device 1, such as
an electronic display, as a matrix of display regions 3, wherein
each display region is associated with, and may comprise, one or
more pixel locations, or groups of pixel locations (i.e., rows,
columns, etc.) associated with distinct image components being
displayed on the image display device. As seen in FIG. 1, a
fundamental image may therefore be represented as a plurality of
distinct fundamental image components F.sub.11-F.sub.MN, where
subscripts "M" and "N" represent the specific pixel(s) location, by
row and column, respectively, of that particular component. It will
be appreciated that individual image components/pixels referenced
throughout the accompanying drawings are shown grossly enlarged for
ease of illustration. In an actual image display device 1, such as
an LCD, the boundaries between adjacent components/pixels are
nearly indistinguishable to the naked eye.
[0048] With reference to the instant invention, providing
confidential viewing of a fundamental image through spatial
multiplexing image modification involves the process of
geometrically combining the fundamental image with another image
for purposes of masking the fundamental image. A periodic (or
random) array of squares, rows, columns, etc., may be removed from
the fundamental image and substituted with corresponding sections
of the masking image, thereby generating a combined image which
obscures the fundamental image from view with the naked eye. When
the images are constructed of pixels, this combining of images can
be on either a pixel by pixel basis, or by groups of pixels.
[0049] While it is certainly contemplated that the masking image
can be of any composition, it is preferred that it be derived from
the original fundamental image, as in the case of an inverse image.
An inverse image is one that, when combined with its fundamental
image, yields a neutral and featureless image When spatially
multiplexing a fundamental image with its inverse image, pixels of
the fundamental image are spatially multiplexed with pixels of the
inverted image.
[0050] This is perhaps shown best in FIGS. 2A, 2B and 2C where, in
accordance with one embodiment of this invention, fundamental image
pixels of a fundamental image are shown spatially multiplexed with
corresponding inverse image pixels derived therefrom. With specific
reference to FIG. 2A, it can be seen that such pixel pairs 5, each
representing a distinct pair of corresponding fundamental and
inverted image components, may be arranged for display on an image
display device 1 in a checkerboard fashion. Alternatively, groups
of pixels associated with corresponding fundamental and inverse
image components may be arranged by pixel rows (FIG. 2B), pixel
columns (FIG. 2C), or even randomly distributed provided the
distance between pixel pairs is not too great. Ideally, however,
the pixels of each pair 5 are directly adjacent to each other.
[0051] Creating such a spatially multiplexed image requires
modification of the original fundamental image to incorporate the
corresponding masking image components. With reference to the
preferred embodiment utilizing inverse image components, for each
fundamental image component (F) utilized, there is required a
corresponding derived inverse image component (I); thus, each
inverse image component requires displacement of an original
fundamental image component from the fundamental image.
[0052] This modification of the fundamental image can be seen in
FIGS. 2A-2C. In FIG. 2A, each pixel location of display 1
represents a separate display region 3.sub.F or 3.sub.I for a
fundamental or inverse image component, respectively, arranged in a
checkerboard fashion. In this arrangement, F.sub.11 denotes the
fundamental image component associated with the pixel 7 located at
row 1, column 1 of the image display device 1. The corresponding
inverse image component I.sub.11 of fundamental image component
F.sub.11 is positioned directly adjacent thereto at pixel location
9, and in this case has positionally displaced what normally would
constitute original fundamental image component F.sub.12 (see FIG.
1). This pattern continues throughout the image display device 1,
thereby causing every other fundamental image component to be
substituted with a corresponding inverse image component of an
adjacently displayed fundamental image component. The resulting
combined image, then, is essentially comprised of a conglomeration
of close, geometrically-intermixed corresponding fundamental and
inverse image components that, when viewed as a whole with the
naked eye, appears neutral and substantially featureless.
[0053] In FIG. 2B, alternating pixel rows now define the associated
display regions 3.sub.F and 3.sub.I of the corresponding
fundamental and inverse image components. In this case, the
fundamental image components F.sub.11-F.sub.1N are displayed in the
first pixel row 11 of the image display device. The corresponding
inverse image components I.sub.11-I.sub.1N, which are derived from
fundamental image components F.sub.11-F.sub.1N, are then displayed
immediately therebelow in the second row of pixels 13, thus
displacing the original fundamental image components
F.sub.21-F.sub.2N at such locations. Similarly, fundamental image
components F.sub.31-F.sub.3N are displayed in the third row of
pixels 15, and their corresponding inverse image components
I.sub.31-I.sub.3N have displaced the original fundamental image
components F.sub.41-F.sub.4N in the fourth row of display pixels
17. Again, this pattern continues throughout the image display
device 1 to create an array of alternating rows of closely adjacent
corresponding fundamental and inverse image components that, when
viewed by the naked eye, will combine to appear neutral and
substantially featureless.
[0054] In much the same manner, in FIG. 2C, alternating pixel
columns of the image display device 1 now comprise the associated
display regions 3.sub.F and 3.sub.I of the corresponding
fundamental and inverse image components. In this case, the
fundamental image components F.sub.11-F.sub.M1 are displayed in the
first pixel column 19 of the image display device. The
corresponding inverse image components I.sub.11-I.sub.M1, which are
derived from fundamental image components F.sub.11-F.sub.M1, are
then displayed immediately adjacent thereto in the second column of
pixels 21, thus displacing the original fundamental image
components F.sub.12-F.sub.M2 at such locations. Similarly,
fundamental image components F.sub.13-F.sub.M3 are displayed in the
third column of pixels 23, and their corresponding inverse image
components I.sub.13-I.sub.M3 have displaced the original
fundamental image components F.sub.14-F.sub.M4 in the fourth column
of display pixels 25. As can be seen in FIG. 2C, this pattern
continues throughout the image display device 1 to create an array
of alternating columns of closely adjacent corresponding
fundamental and inverse image components that, when viewed by the
naked eye, will also combine to appear neutral and substantially
featureless.
[0055] In the above examples, the particular selection and
arrangement of fundamental and inverse image components within the
image display device 1 is not critical, provided the corresponding
components are sufficiently close that the combined image
adequately masks the fundamental image. Thus, it is conceivable
that the display regions 3.sub.F associated with fundamental image
components may be periodically or randomly distributed, or comprise
either odd or even rows or columns of pixels, provided the display
regions 3.sub.I with appropriate derived inverses thereto are
adjacently located so as to be perceived by the naked eye as a
combined substantially featureless image.
[0056] If utilizing inverse image components to mask the
fundamental image, the intensity for each inverted sub-pixel
corresponding to each sub-pixel in the fundamental image is
calculated from;
I.sub.MAX-I.sub.FUND=I.sub.INV,
where I.sub.MAX represents the maximum intensity of the particular
sub-pixel in question, either red, green, or blue; I.sub.FUND
represents the intensity of the particular fundamental sub-pixel in
question; and I.sub.INV is the required intensity for the inverted
sub-pixel in question. It will be appreciated that such calculation
and modification of the fundamental image can be accomplished
internally within an electronic display device using techniques
well known in the art.
[0057] The combined, or multiplexed, image will now have the
overall intensity of;
I.sub.FUND+I.sub.INV=50% Gray,
and appear uniformly neutral and featureless.
[0058] In the foregoing illustrations, the multiplexed fundamental
image components, albeit hidden from public view, are
representative of the original fundamental display image. In order
to provide confidential viewing of the fundamental image
components, and thus the fundamental display image, polarization
encoding is utilized to block the masking image components from the
sight of the authorized viewer, thereby effectively extracting the
fundamental image. Since it is deemed preferable to use fundamental
inverse image components as the masking image components, the
following discussion will focus on this embodiment. It will be
understood, however, that the principles of polarization encoding
discussed herein are not limited to this embodiment, or dependant
in any way on the composition of the masking image components.
[0059] As shown in FIGS. 3A-3C, this system is designed such that
the display regions 3.sub.F of the image display device 1 with
which the fundamental image components are associated are always
cross-polarized relative to the adjacent display regions 3.sub.I
with which the inverse image components are associated. In FIG. 3A,
where the display regions 3.sub.F and 3.sub.I correspond to
alternating individual fundamental and inverse pixels arranged in a
checkerboard fashion, all "fundamental" display regions 3.sub.F are
shown vertically polarized, whereas all "inverse" display regions
3.sub.I are shown horizontally polarized. Similarly, in FIG. 3B,
where the display regions 3.sub.F and 3.sub.I correspond to
alternating fundamental and inverse pixel rows, it is seen that all
"fundamental" rows 3.sub.F are vertically polarized, and all
"inverse" rows 3.sub.I are horizontally polarized. Finally, as
shown in FIG. 3C, alternating pixel columns may also be used to
define the associated display regions 3.sub.F and 3.sub.I of the
corresponding fundamental and inverse image components. In this
system, the "fundamental" columns 3.sub.F are shown vertically
polarized, whereas the "inverse" columns 3.sub.I are shown
horizontally polarized.
[0060] Of course, it will be appreciated that it makes no
difference how the respective display regions 3.sub.F and 3.sub.I
are polarized, provided that they are cross-polarized relative to
each other. Thus, if the display region 3.sub.F associated with
each fundamental image component is polarized in one orientation,
and the display region 3.sub.I associated with each inverted image
component is polarized in an orthogonal orientation, the
fundamental image may be easily extracted, or decoded, by viewing
the combined image through appropriately polarized eyewear 27
constructed to match the state of polarization of the fundamental
image components. In this way, the fundamental image can only be
discerned by those wearing the appropriate eyewear 27.
[0061] Configuring the image display device with adjacent display
regions of differing polarization states may be accomplished by
either incorporating appropriate polarizers directly within the
display pixels of an image display device 1, or by applying
polarizing overlays thereto. In one embodiment, as shown in FIG. 4,
it is contemplated that a micropolarizing overlay 29 having closely
adjacent areas 31, 33 of differing polarization states be
incorporated into an image display device 1, such as an LCD. In
this embodiment, the front or top polarizing layer of the LCD is
actually removed and replaced with the new transparent
micropolarizing overlay 29, which in this case is configured for
row by row cross-polarizing alignment. As shown in FIG. 4, each
distinct display region of the modified LCD panel incorporating
overlay 29 is now associated with one or more rows of either
"fundamental" image pixels or "inverse" image pixels, where each
display region 3.sub.F effectively after the polarization states of
adjacent display regions 3.sub.F and 3.sub.I associated with
corresponding fundamental and inverse image components. In this
embodiment, as shown in FIG. 5, the standard front polarizer 37 of
the LCD need not be removed. Instead, the micropolarizer 35 is
constructed as a 1/2.lamda. phase retarding overlay plate which, in
this case, incorporates alternating rows 39, 41 of etched .lamda.
and 1/2.lamda. steps that align with alternating rows of
corresponding fundamental and inverse image component display
regions 3.sub.F and 3.sub.I.
[0062] The 1/2.lamda. retarder plate 35 can be laminated to the
standard front polarizer 37 of the LCD panel 1 and properly aligned
to effectively rotate the polarization state of alternating pixel
rows or display regions 3.sub.F and 3.sub.I associated with the
fundamental and inverse image components on the LCD panel. In the
embodiment shown in FIG. 5, it is seen that light emitted from each
"fundamental" pixel row or display region 3.sub.F of the LCD panel
1 passes through a 1/2.lamda. phase retardation 41, thereby
shifting the polarization state of such light and associated
fundamental image components by 90 degrees. Light emitted from each
"inverse" pixel row or display region 3.sub.I, on the other hand,
passes through a .lamda. phase retardation 39, thus leaving its
initial polarization unaltered and cross-polarized relative to each
of the display regions 3.sub.F associated with the fundamental
image components. Additionally, it is also contemplated that the
micropolarizer may employ circular polarization, rather than
linear. In the embodiment of FIG. 5, this may be accomplished by
adjusting the plate thickness of the retarder 35 to cause
right-hand circular polarization of one set of display regions
(i.e., 3.sub.F), and left-hand polarization of the other display
regions (i.e., 3.sub.I). Circular polarization eliminates crosstalk
effects which occur if the users head is tilted while viewing
through the polarized eyewear. With circular polarization, the head
may be freely tilted without penalty.
[0063] Of course, it will be appreciated that the micropolarizers
29, 35 described in the above embodiments could equally well be
constructed for column by column cross-polarizing alignment, pixel
by pixel cross-polarizing alignment, or randomly, as previously
suggested. So long as the areas of the micropolarizer that are
aligned with the fundamental image pixels are polarized in a common
state of polarization that is orthogonal or otherwise
cross-polarized relative to the areas of the micropolarizer aligned
with the inverse image pixels, appropriate eyewear 27 passively
polarized to match the polarization state of those areas of the
micropolarizer that are aligned with the fundamental image pixels
may be used to decode the fundamental image.
[0064] It is noted that the use of a micropolarizer 29 having
alternating polarized filters as in FIG. 4, though effective, may
not be as easily produced as the micropolarizer 35 incorporating
the alternating retarders shown in FIG. 5. Also, although it is
contemplated that the present invention may be utilized with all
print and electronic image display devices 1, with respect to
electronic displays, the micropolarizers discussed herein are
likely to be better suited for use in connection with LCD panels,
as the LCD display panel utilizes fixed pixel spacing and is more
adaptable to overlays than say CRT's, which do not have as accurate
control of individual pixel locations.
[0065] In another embodiment, as shown in FIG. 6, an electrically
controllable polarizer 40 can be incorporated in the image display
device 1 to alter the polarization state of the adjacent display
regions 3.sub.F and 3.sub.I associated with the corresponding
fundamental and inverse image components. Such an electronic
polarizer 40 may be used in static or dynamic display systems, and
may take the form of a liquid crystal rotator added to the display
configuration in such manner as to effectively rotate the
polarization angle of transmitted light based on applied voltage
thereto.
[0066] In this embodiment, a second liquid crystal (LC) layer 42 is
laminated to the front panel 37 of the LCD. This second LC layer 42
may be fabricated using known methods in the art, similar to the
LCD, and is constructed having two electrically addressable zones
43 and 45. As shown in FIG. 6, these electrically addressable zones
43 and 45 are constructed from transparent electrodes, such as
indium tin oxide electrodes (ITO), configured in alternating rows
on the inner and/or outer substrates 47 and 49 of the second LC
layer 42.
[0067] Preferably, as shown in FIG. 6, one substrate 47 will carry
alternating ITO rows, with every odd row being interconnected as
one electrically addressable zone 43, and every even row being
interconnected as the second electrically addressable zone 45. The
other substrate 49 may then be configured either as a common ground
for both addressable zones, or separated with matching alternating
ITO rows. In the example shown in FIG. 6, the inner substrate 47 is
shown carrying both addressable zones, and the outer substrate 49
acts as a common ground.
[0068] Suspended between the inner and outer substrates 47 and 49
is the crystalline liquid 51, and depending on the voltage applied
to the respective zones, the light passing through the crystalline
liquid 51 at such location may be rotated so as to effect a change
in polarization thereof. In FIG. 6, the first addressable zone 43
comprising the odd ITO rows is aligned with groups of "fundamental"
pixel rows, while the second addressable zone 45 comprising the
even ITO rows is aligned with groups of corresponding "inverse"
pixel rows. Thus, by applying the appropriate voltage to either the
first or second addressable zone of the second LC layer, the
adjacent display regions 3.sub.F and 3.sub.I associated with the
corresponding fundamental and inverse image components may be
effectively cross-polarized relative to one another.
[0069] Notably, in FIG. 6 the electronically addressable zones 43
and 45 are configured as alternating rows, but it is readily
apparent that these zones can also be arranged in columns, in a
checkerboard pattern, or randomly, to match the pattern of display
regions 3.sub.F and 3.sub.I associated with the respective
fundamental and inverse image components. Depending on the pattern
used, the second LC layer 42 may be made to the exact same
dimensions for perfect alignment. The LC layer 42 acts as an
electrically controllable retarder, providing precise polarization
control to the selected underlying pixels of the LCD 1. For each
display region 3.sub.F or 3.sub.I of the image display device 1,
based on applied voltage thereto, the polarization angle can be set
to rotate transmitted light either 0 or 90 degrees, depending on
whether such display region is associated with fundamental or
inverse image components.
[0070] Although the aforementioned embodiments do provide for
secure viewing of the fundamental image, they are secure only to
the point of having the appropriate passive eyewear 27. More
specifically, anyone wearing eyewear passively polarized to the
same state of polarization as the display regions 3.sub.F
associated with the fundamental image components would be able to
decipher the underlying fundamental image. There are circumstances,
however, where it is desirable to provide a higher level of
security and a more confidential viewing environment.
[0071] One means of providing for enhanced security is to vary the
polarization states of adjacent display regions 3.sub.F and 3.sub.I
using the electrically controllable polarizer 40 described in FIG.
6 above. Since the rotation of light can now be electrically
controlled, it can be used to alter over time the state of
polarization of the respective display regions 3.sub.F and 3.sub.I
associated with the addressable zones 43 and 45 of the second LC
layer 42. From this, it becomes possible to periodically or
randomly vary the state of polarization of the display regions
3.sub.F associated with the fundamental image components.
[0072] Provided the polarized eyewear worn by the authorized viewer
is synchronized to change states of polarization in unison with the
display regions 3.sub.F associated with the fundamental image
components, the polarization of the eyewear will continue to match
that of the display regions 3.sub.F associated with the fundamental
image components, thereby enabling decoding of the fundamental
image. In this embodiment, mere passive polarized eyewear may no
longer be utilized to decode the fundamental image, and thus
security is enhanced.
[0073] A higher level of security may also be obtained using active
polarized eyewear in combination with the passive micropolarizer
overlays 29, 35 previously described. To accomplish this, pixel
position on an electronic display device can actually be made to
alternate between display frames. In other words, the display
position of the fundamental image components may be periodically or
randomly altered to align with fixed areas of polarization
different from that with which they were aligned in the previous
display frame(s).
[0074] For example, shown in FIG. 7 is the display screen of an
electronic image display device 1 incorporating a passive
micropolarizer overlay 29 or 35. In the first frame 53, it is seen
that the fundamental image pixels are displayed in odd rows using
vertical polarization, and the corresponding inverted image pixels
are displayed in even rows using horizontal polarization. In the
next frame 55, the fundamental image pixels switch to the even rows
using horizontal polarization, and the inverted image pixels switch
to the odd rows using vertical polarization. The alternation
between polarization states can be periodic or random. If the
average time at each polarization state is the same, anyone wearing
passive polarized eyewear would see equal amounts of both
fundamental and inverted images, yielding a neutral and
substantially featureless display.
[0075] Notably, in this embodiment, fundamental image components
that are initially suppressed at pixel locations occupied by
inverse image components are revived, and those fundamental image
components previously displayed at other pixel locations become
displaced by new inverse image components derived from the revived
fundamental image components. This can be seen in FIG. 7. In the
first display frame 53, the fundamental image components
F.sub.11-F.sub.1N are present in the top row pixels, and the
corresponding derived inverse image components I.sub.11-I.sub.1N
are present in the second row pizels, thereby displacing the
original second row fundamental image components F.sub.21-F.sub.2N
(see, FIG. 1). In the next display frame 55, however, fundamental
image components F.sub.21-F.sub.2N are revived. The corresponding
derived inverse image components I.sub.21-I.sub.2N now appear in
the top row pixel locations, displacing the initial fundamental
image components F.sub.11-F.sub.1N. Thus, over time the physical
display positions of the corresponding fundamental and inverse
image components are alternated or switched in synch with the
display's refresh rate and in accordance with a predetermined or
random sequence pattern.
[0076] In order to decode the fundamental image in this case,
active polarized eyewear 57 is required. These incorporate
electrically variable polarizers synchronized with the display
device 1. When the fundamental image components are horizontally
polarized, so are the glasses, and when the fundamental image
components switch to vertical polarization, so do the glasses. In
this way, the intended viewer sees only the fundamental image,
while all others see nothing. The active eyewear 57 can be made
wireless as well, and also made to incorporate unique
identification codes so that other active eyewear is unable to
synchronize.
[0077] Another advantage of this active eyewear approach is
recovered resolution. In previous embodiments, one half of the
fundamental image data or pixels were suppressed to allow room for
the inverse image components. For most applications, the typical
resolution of an LCD screen is more than sufficient to accommodate
this loss. But, for high resolution applications, it may be
desirable to have full resolution, as well as a secure viewing
environment. In the embodiment of FIG. 7, resolution is fully
restored through persistence of vision. In the first display frame
53, the fundamental image was taken from all the pixels which were
vertically polarized, with the inverted image being derived from
these. In the second display frame 55, the fundamental image is
taken from the locations which were previously occupied by the
inverted image, and the inverted image pixels are now calculated
from these. In this way, all fundamental image components are
recaptured over time. Therefore, the fundamental image will be
randomly composed of its entire data set, and through persistence
of vision, the fundamental image will appear fully restored.
[0078] In still another more secure and preferable embodiment of my
invention, principles of both spatial and time multiplexation can
be combined to create an image encoding scheme that provides a
highly secure and confidential viewing environment. As shown in
FIG. 8, this too is accomplished using an electronic display device
1 with a passive micropolarizer overlay 29 or 35. Once again,
grouping image components by pixel rows for purposes of
illustration, it is seen that in the first display frame 59, every
odd row of pixels comprise fundamental image components associated
with that specific row (i.e., F.sub.11-F.sub.1N; F.sub.31-F.sub.3N,
etc.). Every even row of pixels, on the other hand, comprise
inverse image components derived from the original fundamental
image components associated with that specific row (i.e.,
I.sub.21-I.sub.2N; I.sub.41-I.sub.4N, etc.). Thus, each
"fundamental" pixel row is spatially multiplexed with an adjacent
"inverse" pixel row, albeit the inverse of the adjacent row of
fundamental image components. While the inverse image components
are not derived from the fundamental image components displayed
directly adjacent thereto, they are likely to be a close
approximation given the relatively gradual change in the overall
color scheme of the fundamental image in comparison to the
miniscule distance between adjacent pixels.
[0079] In the second display frame 61, all image components of the
first display frame 59 are inverted. Thus, all odd rows of pixels
now comprise the corresponding inverse image components of the
original fundamental image components associated with that specific
row (i.e., I.sub.11-I.sub.1N; I.sub.31-I.sub.3N, etc.). Likewise,
all even rows of pixels now comprise fundamental image components
associated with that specific row (i.e., F.sub.21-F.sub.2N;
F.sub.41-F.sub.4N, etc.). As this inversion process continues over
time, every fundamental image component at each pixel location is
not only spatially multiplexed with an adjacent approximate inverse
image component, but is also time multiplexed with its
corresponding derived inverse image component. As in previous
embodiments, it is contemplated that those pixels or groups of
pixels associated with corresponding fundamental and inverse image
components may be arranged by pixel rows (as shown), pixel columns,
or even randomly distributed, as previously described.
[0080] Implementation of the encoding scheme in FIG. 8 can be best
seen by reference to the test image encoding breakdown shown in
FIG. 9. As shown therein, a fundamental test image 65 comprising a
happy face, geometric figures and textual matter may be represented
as two display frames (Frame 1 and Frame 2) alternating in time on
a typical electronic image display device 1. The first display
frame (Frame 1) of the fundamental image 65 is shown further broken
down into a display 67 of "odd row" fundamental image components
(i.e., F.sub.11-F.sub.1N; F.sub.31-F.sub.3N, etc.) and a display 69
of "even row" inverse image components (i.e., I.sub.21-I.sub.2N;
I.sub.41-I.sub.4N, etc.) which, when combined, creates a relatively
obscure spatially combined image 71 of fundamental and inverse
image components.
[0081] The second display frame (Frame 2) of the fundamental image
65 is shown further broken down into a display 73 of "even row"
fundamental image components (i.e., F.sub.21-F.sub.2N;
F.sub.41-F.sub.4N, etc.) and a display 75 of "odd row" inverse
image components (i.e., I.sub.11-I.sub.1N; I.sub.31-I.sub.3N, etc.)
which, when combined, creates another relatively obscure spatially
combined image 77 of fundamental and inverse image components that
is the true inverse of the spatially combined image 71 of the first
display frame.
[0082] Since the spatially combined images 71 and 77 are the true
inverses of one another, alternating such images over time
generates a resulting combined image 79 that appears substantially
featureless and neutral to the naked eye, thereby masking the
fundamental image from the sight of all unauthorized viewers. As
described previously in connection with FIG. 7, decoding of the
fundamental image may be effected using similar active polarized
eyewear 63, thus providing for enhanced security. Because
fundamental image components align with different display regions
3.sub.F during successive display frames (i.e., even versus odd
pixel rows), synchronized eyewear 63 can be made to alter states of
polarization to match the polarization state of the display regions
3.sub.F associated with the fundamental image components currently
being displayed.
[0083] Also, as in the embodiment of FIG. 7, such multiplexing of
the fundamental and inverse images in FIGS. 8 and 9 may occur in
accordance with a predetermined or random sequence pattern.
Provided the average time at each polarization state is the same,
anyone wearing passive polarized eyewear would still see equal
amounts of both fundamental and inverted images, yielding a neutral
and substantially featureless display. Moreover, as in the
embodiment of FIG. 7, full resolution of the fundamental image will
be completely restored through persistence of vision, as all
fundamental image components are recaptured over time.
[0084] Although less secure, it is also contemplated that the use
of an electrically controllable polarizer 40 as described in FIG. 6
could be combined with the systems of either FIG. 7 or FIG. 8 to
operate in synch with the alternating display positions of the
fundamental image components, thereby providing a system that may
be decoded using passive polarized eyewear with full resolution of
the decoded fundamental image. This may be advantageous in
applications where a lower level of security is acceptable, but
high resolution is required.
[0085] To provide an even more secure environment, overlay or
misleading images may be incorporated. In systems utilizing masking
inverse image components, such overlay components may be simply
added to the derived inverse image components. Thus, casual
observers will see something other than neutral gray, and something
entirely different than the fundamental image. Since the overlay
image components are incorporated as part of the displayed inverse
image components, the dynamic range of the inverse image components
must be compressed to allow for the addition of the overlay image.
Consequently, in order to maintain neutrality of the background to
the overlay image, the dynamic range of all corresponding
fundamental image components must also be compressed
proportionately to account for the addition of the overlay image.
In other words, the dynamic range of the fundamental image must be
reduced by the dynamic range of the overlay image to maintain
complete masking of the fundamental image. With the overlay image
components being added to the inverse image components, they too
will be blocked from the view of an authorized viewer wearing the
appropriately polarized eyewear matching the polarization state of
the display regions associated with the fundamental image
components.
[0086] When applied to print media, confidential images may be
embedded within other misleading images. In much the same way as
described above, the fundamental image pixels and the inverted
image pixels are printed and then laminated with a micropolarized
overlay. Now, viewing the fundamental image is only possible while
wearing the appropriate eyewear.
[0087] As can be seen by the foregoing, through modification of the
fundamental image, fundamental and masking image components may be
spatially multiplexed for display in association with adjacent but
cross-polarized display regions of an image display device. By
utilizing masking "inverse" image components, a highly secure
combined image may be generated that will appear neutral and
substantially featureless to the naked eye, and if desired,
misleading overlay images may be incorporated. With appropriately
polarized eyewear, this combined image may be demultiplexed for
confidential viewing of the fundamental image. As shown, this may
be accomplished without the need for high speed multiplexing of
image signals, or cumbersome, cost-intensive supplemental and/or
wavelength-shifted masking light sources.
[0088] It will, of course, be understood that various changes may
be made in the form, details, arrangement and proportions of the
parts without departing from the scope of the invention which
comprises the matter shown and described herein and set forth in
the appended claims.
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